1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer and a copier.
2. Description of the Related Art
Hitherto, there have been known various image forming apparatuses adopting electro-photographic or electrostatic recording system in their image forming process, and as one example of these various image forming apparatuses, there is a tandem type image forming apparatus in which a plurality of process cartridges is arrayed in a row along a rotational direction of an intermediate transfer belt rotatably stretched and which is configured to form a color image through the intermediate transfer belt.
This type of full-color image forming apparatus includes a photoconductor cleaning blade removing residual toner left on the photoconductive drum (image carrier) after a primary transfer and a second cleaning blade removing residual toner left on the intermediate transfer belt after a secondary transfer.
As such a cleaning blade, a counter-type cleaning blade made of an elastic material such as rubber is brought into contact so as to face in a driving direction is adopted in general. This counter-type blade cleaning is known to cause a problem called turn-up of the blade in a case where friction forces between the cleaning blade and the photoconductive drum and between the cleaning blade and the intermediate transfer belt increase.
Then, conventionally, Japanese Patent Application Laid-open Nos. 2004-258419 and 2005-106920 disclose to avoid the occurrence of the turn-up of the blade or the like by supplying lubricant to nip portions between the cleaning blade and the photoconductive drum and the cleaning blade and the intermediate transfer belt to reduce the friction forces.
Specifically, Japanese Patent Application Laid-open No. 2004-258419 discloses to detect a driving torque of a photoconductive drum by a current detecting portion, and based on the detection result, to determine an abnormality of the cleaning blade of a cleaning unit, and to supply lubricant toner to avoid the abnormality.
Japanese Patent Application Laid-open No. 2005-106920 discloses to change a length in a sub-scan direction of a toner belt in a case where a print set number is less than a first reference value. That is, JPA No. 2005-106920 discloses to change the length in the sub-scan direction of the toner belt corresponding to a total number of pixels drawn into a predetermined length of an area from both ends of the cleaning blade during preparation of a most recent total number within a second reference value of prints and to an intra-apparatus temperature just before forming the toner belt.
By the way, while both JPA Nos. 2004-258419 and 2005-106920 describe the image forming apparatuses configured to prevent turn-up of the blade from occurring by supplying lubricant toner for the cleaning blade cleaning the photoconductive drum, there is a case where such cleaning blade is provided for the intermediate transfer belt as described in JPA No. 2005-106920.
In such a case, if a friction between the cleaning blade and the intermediate transfer belt increases, there is a possibility that the turn-up of the cleaning blade cleaning the intermediate transfer belt occurs as well. However, no consideration is made concerning the possibility of causing the turn-up of the cleaning blade for the intermediate transfer belt in the image forming apparatuses described in JPA Nos. 2004-258419 and 2005-106920.